In the nuclear or chemical industry, when the industrial installations concerned are shut down, various maintenance, repair or servicing operations are carried out on the fluid circulation circuits.
In operation, certain circuits of the same installations carry products and materials which are toxic, contaminating or polluting, and it is not sufficient to have entirely evacuated the pipes, valves or chambers on which an operator has to take action, in order to protect that operator against any contact with the toxic products. Furthermore, at any open place of the circuit, within which the operator takes action, it is necessary to aspirate permanently the internal atmosphere, in order to direct a residual toxic gaseous flow away from the person taking action.
An example taken from the nuclear industry will enable the constraints expressed previously to be understood. When a nuclear power station is shut down, after having evacuated the primary cooling circuit, action is taken at various open places of the latter, for example in the opening of a valve, to undertake manually various repair or servicing operations. The internal residual atmosphere, within the open circuit, remains contaminating, in the sense that it can be assimilated to a suspension of radioactive particles, even if the radioactivity of the latter is frequently of short life.
Such action must therefore be taken while protecting the body of the person taking action against any contact with this contaminating residual atmosphere.
To this end, in accordance with U.S. Pat. No. 3,437,558, and more particularly in accordance with the embodiment described with reference to FIG. 4 of the latter, a containment device has been proposed, comprising:
a means for collecting by aspiration, which means is placed in position on the border of the orifice of the opening cavity, in the specific case the open vessel of a nuclear reactor; this collecting means comprises two collecting rings disposed opposite one another on the said border, but separated from one another, having together a profile open along a diameter of the circular opening of the reactor, this profile corresponding to the contour of the border of the latter; each ring has a U-shaped cross-section open towards the interior of the reactor, and comprises a plurality of aspiration openings, in all cases directed towards the interior of the reactor;
a plurality of outlet conduits each communicating, at one end, with a single evacuation conduit, connected to a vacuum means, and, at the other end, with the opening of a collector.
This device, consisting of rigid elements, is installed at a fixed station throughout the entire duration of the works. As such, this device cannot be used in a mobile works, repeatedly necessitating the assembly and the demounting, by the operator, of any dynamic containment device. Moreover, the placing in position of the latter must be undertaken rapidly, in order to limit the materials taken in by the operator in an ionizing environment.